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Activities involved Software Development life cycle model

Problem solving in software consists of these activities:
  1. Understanding the problem

  2. Deciding a plan for a solution

  3. Coding the planned solution

  4. Testing the actual program

For small problems these activities may not be done explicitly. The start end boundaries of these activities may not be clearly defined, and not written record of the activities may be kept. However, for large systems where the problem solving activity may last over a few years. And where many people are involved in development, performing these activities implicitly without proper documentation and representation will clearly not work. For any software system of a non-trival nature, each of the four activities for problem solving listed above has to be done formally. For large systems, each activity can be extremely complex and methodologies and precedures are needed to perform it efficiently and correctly. Each of these activities is a major task for large software projects.

Furthermore, each of the basic activities itself may be so large that it cannot be handled in single step and must be broken into smaller steps. For example, design of a large software system is always broken into multiple, distinct design phases, starting from a very high level design specifying only the components in the system to a detailed design where the logic of the components is specified. The basic activities or phases to be performed for developing a software system are:

  1. Requirement Analysis / Determination of System's Requirements

  2. Design of system

  3. Development (coding) of software

  4. System Testing

In addition to the activities performed during software development, some activities are performed after the main development is complete. There is often an installation (also called implementation) phase, which is concerned with actually installing the system on the client's computer systems and then testing it. Then, there is software maintenance. Maintenance is an activity that commences after the software is developed. Software needs to be maintained not because some of its components "wear out" and need to be replaced, but because there are often some residual errors remaining in the system which must be removed later as they are discovered. Furthermore, the software often must be upgraded and enhanced to include more "features" and provide more services. This also requires modification of the software, Therefore, maintenance in unavoidable for software systems.

In most commercial software developments there are also some activities performed before the requirement analysis takes place. These can be combined into a feasibility analysis phase. In this phase the feasibility of the project is analyzed, and a business proposal is put forth with a very general plan for the project and some cost estimates. For feasibility analysis, some understanding of the major requirements of the system is essential. Once the business proposal is accepted or the contract is awarded, the development activities begin starting with the requirements analysis phase.

Following topics describes the above mentioned phases:

  1. Preliminary Investigation

  2. Requirement Analysis / Determination of System's Requirements

  3. Design of system

  4. Development (coding) of software

  5. System Testing

  6. Software Maintenance

  7. Error distribution with phases

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